Technical Field
The present invention relates to audio equipment and, more particularly, to input and output terminals of the same.
Related Art
Although various types of audio equipment have hitherto been equipped with input terminals and output terminals, each of the terminals requires a footprint. Hence, when miniaturization of portable equipment is sought, the footprints might cause a hindrance to miniaturization.
JP S64-003374 U describes determining whether a terminal connected to a video input/output terminal is an input terminal or an output terminal by detecting a difference between d.c. impedance of the input terminal and d.c. impedance of the output terminal of the video input/output terminal; and automatically switching between the input and the output of the video input/output terminal.
JP H11-239289 A describes standardizing an input terminal of a digital video signal and an output terminal of an analog video signal or standardizing an output terminal of the digital video signal and an output terminal of the analog video signal, thereby integrating the terminals of a still picture imaging device.
JP 2001-086416 A describes realizing a shared use of an external video input terminal and an external video output terminal and a shared use of an external audio input terminal and an external audio output terminal; and automatic or manual switching between the input terminals and the output terminals if the user desires.
However, the related-art techniques provide only standardization of two terminals; namely, the input terminal and the output terminal or the analog terminals and the digital terminals, without attaining standardization of a larger number of terminals.
Particularly in recent years, portable headphone amplifying devices have been developed with a view toward fulfilling users' desires to play music data stored in a smartphone, and others, and listen to music with high quality through headphones. In order to cope with a variety of devices, some headphone amplifying device are often equipped with an analog input terminal, a digital coaxial input terminal, a digital coaxial output terminal, and an optical input terminal as well as a USB connector for connection with a smartphone and an analog output terminal for connection with a headphone. A problem is how to standardize the variety of terminals.